title: Trans-translation mediates tolerance to multiple antibiotics and stresses in Escherichia coli.
abstract: BACKGROUND
  Trans-translation mediated by SsrA (tmRNA) and its associated protein SmpB plays an important role in rescuing stalled ribosomes and detoxifying toxic protein products under stress conditions. However, the role of SsrA and SmpB in bacterial persister survival has not been studied. The recent finding that pyrazinamide as a unique persister drug inhibits trans-translation in Mycobacterium tuberculosis prompted us to examine the role of trans-translation in persister survival.
  
  
  METHODS
  Using Escherichia coli as a model, we constructed SsrA and SmpB mutants and assessed the susceptibility of the mutants to various antibiotics and stress conditions in MIC/MBC and persister assays.
  
  
  RESULTS
  We found that mutations in SsrA and SmpB caused a defect in persister survival as shown by their increased susceptibility to a variety of antibiotics, including gentamicin, streptomycin, amikacin, norfloxacin, trimethoprim and tetracycline, and also stresses, such as acid, weak acid salicylate, heat and peroxide. Additionally, the SsrA and SmpB mutants were 2-8-fold more susceptible than the parent strain to various antibiotics in MIC and MBC tests. The SmpB mutant was more susceptible to antibiotics and stresses than the SsrA mutant. A particularly interesting finding is the hypersusceptibility of the SmpB mutant and the SsrA mutant to trimethoprim. The defect of various SsrA and SmpB mutant phenotypes could be complemented by functional ssrA and smpB, respectively.
  
  
  CONCLUSIONS
  We conclude that SsrA and SmpB are important for persister survival and may serve as a good target for developing new antibiotics that kill persister bacteria for improved treatment of persistent bacterial infections.
authors.affiliation: Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Jinghua
authors.initials: J
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Ji
authors.forename: Wanliang
authors.initials: W
authors.lastname: Shi
authors.forename: Jianping
authors.initials: J
authors.lastname: Xie
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000143:Acids / Q000633:toxicity; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004361:Drug Tolerance; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D017353:Gene Deletion; D006358:Hot Temperature; D006801:Humans; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D016877:Oxidants / Q000633:toxicity; D014176:Protein Biosynthesis; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D000143:Acids; D000900:Anti-Bacterial Agents; D016877:Oxidants; D016601:RNA-Binding Proteins; C430328:small protein B
keywords: drug target; drug tolerance; persistence; persister mechanisms; persisters